What is IGF-1 LR3?
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a recombinant analogue of human IGF-1 in which an arginine is substituted at position 3 and a 13-amino-acid extension peptide is added to the N-terminus. These modifications dramatically reduce binding to IGF-binding proteins (IGFBPs), extending the half-life from the ~15 minutes of native IGF-1 to approximately 20–30 hours. It has been widely used in cell culture and animal research to study anabolic signaling, satellite cell activation, and tissue repair.
Mechanism of action
IGF-1 LR3 binds the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase, activating PI3K/Akt and MAPK/ERK signaling cascades. This drives protein synthesis, inhibits apoptosis, and promotes satellite cell proliferation — processes central to muscle hypertrophy and tissue repair models.
Researched benefits
- Enhanced skeletal muscle protein synthesis in animal models
- Satellite cell activation and myoblast proliferation studied in vitro
- Accelerated recovery from exercise-induced muscle damage in rodent work
- Connective tissue and cartilage repair signaling
- Neuronal survival and neurite outgrowth in preclinical neuroprotection studies
Researched dosage
Most research protocols use 20–100 mcg administered 1× per day via subcutaneous injection. Research protocols report doses of 20–100 mcg subcutaneously or intramuscularly once daily, typically post-exercise in muscle-focused studies. Short cycles (4 weeks on, 4 weeks off) are common due to concerns about receptor desensitization.
A typical cycle runs 4 weeks on, then 4 weeks off before reassessment.
Use the calculator below to convert your target IGF-1 LR3 dose into exact insulin-syringe units.
Reconstitution & storage
A standard 1 mg vial reconstituted with 2 mL of bacteriostatic water yields 500 mcg/mL. Store lyophilized vials at -20°C for long-term stability; short-term storage at 2–8°C is acceptable. Reconstituted solution should be refrigerated and used within 14–21 days.
Side effects & considerations
- Hypoglycemia risk, particularly when dosed without food (IGF-1 has insulin-like activity)
- Facial and jaw swelling with prolonged use (acromegalic-type effects at high doses)
- Potential for enhanced growth of pre-existing tumors due to IGF-1R stimulation
- Injection-site discomfort
IGF-1 LR3 stacks
- Anabolic Recovery Research — paired with BPC-157. Combined anabolic signaling and tissue repair. Preclinical work has combined IGF-1 LR3 with BPC-157 to model the interaction between IGF-1 receptor-driven growth signals and BPC-157's angiogenic and gut-protective actions in recovery contexts.
- GH Axis Completion — paired with CJC-1295, Ipamorelin. Upstream GH stimulation with direct IGF-1 supplementation. Some researchers pair GH secretagogues (which raise IGF-1 indirectly) with exogenous IGF-1 LR3 to study both arms of the GH/IGF-1 axis simultaneously.
Selected research
- Long R3 IGF-I: A super-potent analogue of IGF-I — Biochemistry and Cell Biology, 1992
- IGF-1 splice variants and muscle growth — Journal of Physiology, 2004
- Role of IGF-1 in skeletal muscle hypertrophy and atrophy — Endocrinology, 2009